DEC Mouse replacement

[Douglas Taylor]

I had run into those bits on the web and also a ps2 driver for the 
arduino on github.
The protocols are similar for the PS2 mouse and the DEC mouse, 3 bytes 
encoded with movement data.

Generic PS/2 Mouse Packet Bits
BYTE    7    6    5    4    3    2    1    0
0    yo    xo    ys    xs    ao    bm    br    bl
1    xm
2    ym
Code    Description
yo    Y-Axis Overflow
xo    X-Axis Overflow
ys    Y-Axis Sign Bit (9-Bit Y-Axis Relative Offset)
xs    X-Axis Sign Bit (9-Bit X-Axis Relative Offset)
ao    Always One
bm    Button Middle (Normally Off = 0)
br    Button Right (Normally Off = 0)
bl    Button Left (Normally Off = 0)
xm    X-Axis Movement Value
ym    Y-Axis Movement Value

DEC mouse bits  (4800 Baud RS232)
BYTE    7    6    5    4    3    2    1    0
0    1   0   0  sx  sy  l m r
1    xm
2    ym
Code    Description
sy    Y-Axis Sign Bit
sx    X-Axis Sign Bit
ao    Always One
l,m,r  Left, Middle, Right button
xm    X-Axis Movement Value
ym    Y-Axis Movement Value

This level of similarity made me think that a simple controller like the 
arduino could easily handle this.

Doug


On 5/4/2018 3:13 AM, mark--- via cctalk wrote:
> The Linux Kernel has support for DEC VSXXX mouse (as well as LK keyboards), the opposite of what you are interested in.
> So the conversion from DEC protocol is well documented.
> It would be fairly straightforward with a microcontroller to implement the reverse.
>
> See: https://code.woboq.org/linux/linux/drivers/input/mouse/vsxxxaa.c.html
>
> The major issue implementing support for DEC mice under Linux is the requirement for a -12v power rail - clearly this isn't an issue with a modern day replacement (I suspect it is a red-herring anyway for standard mice, just because-12v exists at the DEC connector doesn't mean it is used, possibly it was for digitizers for example).
>
> The DEC mouse protocol is described here: http://oldcomputers.dyndns.org/public/pub/rechner/dec/manuals/decimages/104aatm1.pdf, section C6 onwards.
>
> Regards, Mark.
>
> -----Original Message-----
> From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Bill Degnan via cctalk
> Sent: Friday, May 4, 2018 3:06 AM
> To: Douglas Taylor <dj.taylor4 at comcast.net>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
> Subject: Re: DEC Mouse replacement
>
> On Thu, May 3, 2018, 9:38 PM Douglas Taylor via cctalk < cctalk at classiccmp.org> wrote:
>
>> I would like to have a couple more DEC Mice for some Vaxestations I
>> have, but they seem to be pretty rare.  At present I only have one
>> mouse and I move it from machine to machine.
>>
>> The protocols for the DEC mice and the standard PS/2 mice don't seem
>> to be that much different.
>>
>> Is it possible to use an arduino to translate  PS/2 mouse output and
>> then send it to the vaxstation so that will it mimic a classic DEC mouse?
>>
> The jack is different, that would be a factor too.
> B
>